In the event of the vehicle crashing, it is appropriate to protect the physical integrity of passengers in the vehicle, and in particular to avoid a crushing phenomenon. In order to dissipate the energy due to the crash of the vehicle, seat manufacturers have opted for devices that dissipate the kinetic energy of the seat by crushing an element.
Document EP 0 814 020 describes a first seat of that type. According to document EP 0 814 020, a crashworthy seat for a vehicle comprises a pan and a stand for connecting the pan to the floor of the vehicle, the pan being provided with a seat proper and a seat back for receiving an individual. The stand is provided with first and second feet each extended by a vertical support element having a respective longitudinal rib. Furthermore, the back of the pan supports one fastener element per vertical support element. Consequently, each rib is engaged in a channel of the associated fastener element, the portion of the rib situated above the fastener element being of a cross-section that is smaller than the portion of the rib situated below said fastener element. In the event of the vehicle, e.g. a helicopter, crashing, the downward movement of the vehicle is stopped violently and suddenly when the vehicle makes contact with the ground. Because of its inertia, the assembly comprising the pan and the individual thereon tends to continue moving downwards and the fastener elements slide along the ribs which then act as guide means. Furthermore, the fastener elements plane or shave the rib as they move downwards, thereby enabling said rib to perform the function of an energy absorber, specifically absorbing the energy resulting from the kinetic energy of the pan and the individual occupying it. Consequently, the deceleration to which the pan and said individual is subjected is reduced significantly by the ribs of the vertical support elements.
That first seat thus provides means acting both as guide means and as absorber means, with the removal of material from said absorber means turning out to be very effective. Nevertheless, after a crash, the vertical support elements and the fastener elements need to be replaced, which gives rise to non-negligible costs.
Document EP 0 078 479 discloses a second crashworthy seat provided with a first structure having a pan and a frame fastened to the pan. In addition, the second seat is provided with two columns suitable for being fastened to structural parts of a vehicle. The frame has two sleeves, each sleeve being suitable for sliding on a respective column, thus performing the function of guide means.
In order to prevent the sleeves sliding under normal conditions, the seat has a plurality of bars fastened at their top ends to cap members arranged on the top ends of the columns. More precisely, the seat has one cap member per column, with each cap member being fitted with four bars. Furthermore, each column is surrounded by a drawing die, itself surrounded by a collar. The bars of a column pass through a drawing passage formed in the drawing die of the column. It should be observed that the diameter of each bar below the drawing die is larger than the diameter of the drawing passage. Consequently, as for the first seat, in the event of the pan moving downwards rapidly as the result of a crash, the bars are deformed by the drawing die, thus enabling a large amount of energy to be absorbed.
In contrast, the guide means, i.e. the columns, are here dissociated from the absorber means, i.e. the bar. After the crash, only the bars and the drawing matrix need to be changed, and that enables costs to be limited. Nevertheless, in practice, such replacement requires the seat to be completely dismantled. Furthermore, the fabrication costs of the seat remain relatively large because of their close fabrication tolerances.